The invention relates to a method for reeling up, in which a paper web or the like is continuously reeled on a reeling core, wherein the formation of the paper reel is controlled at least by means of
an actuator of the reeling core, advantageously by means of a centre-drive,
an actuator of a primary surface drive device of the paper reel, advantageously by means of a centre-drive, and
a nip load effective between the outer perimeter of the paper reel formed on the reeling core and the outer perimeter of the primary surface drive device of the paper reel the nip load being produced by means of an actuator, a so-called nip load device.
As for the state of art, reference is made to the publication EP-483092, which discloses a centre-drive assisted reel-up. In addition, with regard to the state of art, it can be stated that the document WO-A-99/42392 discloses a method for reeling up, in which the reeling is controlled by adjusting the torque in the centre-drives. This, however, takes place in a manner which is not described in more detail.
In particular, the control of the drives of the reel-up in a paper machine takes place in such a manner that the speed of rotation of the primary surface drive device of the paper reel is adjusted so that the desired web tension is maintained between the reel-up and the preceding machine part (e.g. a drying section or a machine calender) exerting tensile stress on the paper web, and the torque of the drive of the reeling core is adjusted in such a manner that a suitable torque compensating the low speed of the mass of the paper reel that is being formed is thereby maintained. The adjustment of the torque is based on empirical information and the torque is changed in accordance with predetermined guidelines when the reeling up process proceeds to the reeling core. The tension of the paper web can be utilized to affect the density of the paper reel that is being formed. However, the act of increasing the tension of the paper web i.e. the act of increasing the tension difference for the primary surface drive device of the reel results in an increasing risk of paper web breaks, and possibly also causes stretching which otherwise impairs the properties of paper.
Thus, the solution of prior art is clearly limited in view of the overall control of the reeling up process. The present technology, for example the increased web speeds, set even higher demands for the methods for adjusting the process. The preset control of the centre torque does not take into account the real needs of the manufacturing process actively or in real time and neither does it take into account the possible changes occurring in the process during the reeling up. In particular, this applies to such interference situations which could be handled by means of a better control of the paper web, but which in the control according to the present state of art result in breaks in the paper web.
It is an aim of the present invention to eliminate the above-presented problems to a large extent thereby improving the state of art prevailing in the field. By means of the method according to the invention, it is possible to affect the formation of the paper reel in the reel-up when the reeling up process proceeds, and to produce such changes in the reeling up which eliminate the web break otherwise produced in connection with conventional methods. Thus, by means of the invention it is also possible to attain advantages while runnability becomes more reliable and continuity is improved therein.
To attain the above-described objectives, the method according to the invention is primarily characterized in that the torque produced by means of the actuator of the primary surface drive device of the paper reel is selected so that it is smaller than the sum of the torque values produced by the actuators driving the paper reel that is being formed.
As a whole, by means of the method according to the invention for reeling up, it is possible to implement a reeling process in such a manner that
the torque of the drive of the primary surface drive device of the paper reel can be substantially set merely according to the tension requirements of the paper web before the reel-up, wherein the measurement information on the tension of the paper web is transferred to a control computer in real time, and the torque of the drive in the primary surface drive device of the paper reel is adjusted on the basis of this measurement information. This partial adjustment can be implemented without paying attention to the manner in which it will affect the density and other properties of the paper reel that is being formed, and
the tension of the paper web between the paper layers inside the paper reel that is being formed is adjusted by controlling the other drives affecting the paper reel in relation to the torque of the drive of the surface drive device, wherein both the tension of the paper web before the reeling up stage and the tension of the paper reeled on the paper reel can be optimised comprehensively in real time in the reeling process.